ABSTRACT Canine transmissible venereal tumour (CTVT) is a naturally occurring transmissible neoplasm with variable biological behaviour, including progressive growth, stationary behaviour and spontaneous regression. However, the marker‐expression patterns associated with these clinicopathological phenotypes remain incompletely characterised. The present study investigated iNOS, PCNA and p53 expression in CTVT and evaluated their association with the operational clinicopathological phenotype. Sixteen genital CTVT samples obtained from surgically treated dogs were classified as stable ( n = 7) or progressive ( n = 9) using predefined criteria requiring concordance between local invasion and quantitative mitotic count. Immunohistochemistry was performed for iNOS, PCNA, p53 and cytokeratin (CK), and immunoreactivity was evaluated semiquantitatively by two blinded observers. Progressive tumours showed significantly higher iNOS, PCNA and p53 immunoreactivity scores than stable tumours. Across the three markers, median scores ranged from 0 to 1 in stable tumours and were 3 in progressive tumours, with significant differences in all comparisons (Mann–Whitney U = 0.0; two‐sided exact p = 0.0002). iNOS immunoreactivity was predominantly cytoplasmic in tumour cells, with occasional staining in vascular endothelial and inflammatory cells, whereas PCNA and p53 showed widespread nuclear positivity in progressive tumours and more limited expression in stable tumours. CK immunoreactivity was absent in all samples, consistent with the absence of detectable cytokeratin expression in the examined tumours. To our knowledge, the present study provides the first tumour‐cell‐focused characterisation of iNOS immunoreactivity in CTVT, evaluated concurrently with PCNA and p53 across operationally defined stable and progressive clinicopathological phenotypes.
ABSTRACT Electrochemotherapy is increasingly used as a locoregional treatment for feline squamous cell carcinoma, but its role in advanced nasal planum disease remains poorly defined. This retrospective study evaluated the long‐term outcome of ECT as a sole treatment modality in 18 cats with T 3 –T 4 N 0 M 0 nasal planum squamous cell carcinoma. Adverse events were assessed according to VCOG‐CTCAE v2. Response was assessed using RECIST v1.1 criteria, and progression‐free survival (PFS), overall survival (OS) and time to progression (TTP) were analysed using Kaplan–Meier methods. At the end of treatment, 72.2% of cats achieved complete response, 16.7% partial response and 11.1% stable disease, resulting in an overall response rate of 88.8%. The 1‐year complete response rate was 61.1%. Treatment response was significantly associated with PFS ( p = 0.006), OS ( p < 0.001) and TTP ( p = 0.006), while recurrence was associated with shorter PFS ( p = 0.003) and OS ( p = 0.002). The 1‐year risk of recurrence was 50%. Adverse events were mostly low‐grade (VCOG Grade I–II) and self‐limiting, the most common being transient local pain, erythema/crusting and pruritus; no grade ≥ 3 complications such as tissue necrosis or fistula formation were observed. These results suggest that ECT is an effective and well‐tolerated treatment also in advanced stages nasal planum squamous cell carcinoma, with high response rates and long‐term control disease. The risk of recurrence underscores the need for prolonged follow‐up, as additional treatment sessions may be performed upon relapse, while ECT can also be used with palliative intent to prolong survival while preserving quality of life.
Lymphoma is a common canine malignancy with high morbidity and variable prognosis. Circulating tumour DNA (ctDNA) has emerged as a minimally invasive biomarker for tumour burden, treatment response and prognosis in human lymphoma. However, the feasibility of applying shallow whole-genome sequencing (sWGS)-based ctDNA analysis to canine lymphoma remains unclear. In this pilot study, plasma cell-free DNA (cfDNA) was quantitatively assessed and additional genomic features were evaluated using sWGS in dogs with multicentric lymphoma. cfDNA concentration was significantly higher in dogs with lymphoma (n = 13) compared with healthy controls (n = 24) (median 3.18 vs. 0.25 ng/mL; Mann-Whitney U test, p = 0.004). However, total cfDNA concentration was not significantly associated with time to progression (TTP) (p = 0.055). Tumour fraction (TF), a surrogate for ctDNA, showed preliminary association with clinical outcome, with a shorter median TTP in the high-TF group than in the low-TF group (77 vs. 302 days; p = 0.006). Genomic analysis further revealed copy number aberrations (CNAs); notably, gains on chromosome 13 containing the MYC locus were identified in three dogs, all of which belonged to the high-TF group. Dogs with lymphoma also displayed distinct cfDNA fragmentation profiles, characterized by an enrichment of shorter fragments within the analysed size range and a shift in the highest mean-profile peak compared with healthy controls. These findings demonstrate the feasibility of sWGS-based cfDNA analysis in canine lymphoma and suggest that TF may provide clinically relevant information beyond total cfDNA concentration. Validation in a substantially larger, independent cohort is warranted.
ABSTRACT Conventional cancer cell lines often fail to capture tumour heterogeneity, limiting their translational relevance for radiation response studies. This study aimed to establish a low‐passage, patient‐derived heterogeneous culture and to evaluate its radiation response characteristics. Tumour tissue obtained from a canine oral melanoma patient was used to generate the culture. Cellular heterogeneity was confirmed by morphological features and the expression of stem cell‐associated markers (CD133 + CD44 + : 50.53% ± 5.05%, CD133 − CD44 + : 30.93% ± 7.21%). Tumorigenicity was validated using a xenograft model. Radiation responses to 2 and 10 Gy were assessed using clonogenic survival, viability, proliferation, apoptosis, DNA damage, migration, and invasion assays. The culture demonstrated morphological heterogeneity, expression of stem cell‐associated markers, and tumorigenic potential in vivo. Compared with the 0 Gy control, 10 Gy irradiation significantly reduced cell viability, proliferative activity, and migration, while increasing early apoptosis and DNA damage (all p < 0.006). These effects were generally more pronounced after 10 Gy than after 2 Gy. Notably, clonogenic survival curves deviated from the linear‐quadratic model, indicating non‐classical radiation response behaviour in heterogeneous cell populations. This proof‐of‐concept study suggests that a low‐passage, patient‐derived heterogeneous culture may serve as a practical and biologically informative in vitro platform for investigating radiation responses in canine oral melanoma. Further validation using additional patient‐derived cultures and comparisons with corresponding clinical radiation responses is needed.
ABSTRACT Feline intermediate‐ to large‐cell lymphoma is commonly treated with COP or CHOP chemotherapy, but the clinical benefit of adding doxorubicin (CHOP) remains controversial given its associated toxicity profile and cost. This systematic review and exploratory meta‐analysis summarized response and survival outcomes reported for COP‐ and CHOP‐based protocols in feline intermediate‐ to large‐cell lymphoma. Searching PubMed, Scopus, and CAB Abstracts (2000–2024), we included 21 studies comprising 1054 cats. An exploratory random‐effects meta‐analysis utilizing Restricted Maximum Likelihood (REML) estimation was conducted to evaluate overall (ORR), complete (CR), and partial response (PR) rates. The overall pooled ORR was 81.0%. Subgroup meta‐regression revealed no statistically significant differences between COP and CHOP for ORR (83.0% vs. 77.0%, p = 0.360), CR (57.0% vs. 49.0%, p = 0.350), or PR (28.0% vs. 22.0%, p = 0.468). Profound heterogeneity (overall I 2 = 85.4%–89.6%) persisted across all analyses, driven primarily by the pooling of diverse anatomical subtypes and uncontrolled confounding by Feline Leukaemia Virus (FeLV) status. Furthermore, inadequate variance reporting and a widespread lack of standardized response criteria (e.g., VCOG‐RECIST) precluded a formal meta‐analysis of survival outcomes. Descriptively, reported median survival times ranged broadly (COP: 108–610 days; CHOP: 62–973 days) without a clear advantage for CHOP. A custom weighted risk‐of‐bias assessment highlighted significant methodological deficiencies across the literature. In conclusion, current aggregate evidence does not demonstrate a statistically detectable difference in response rates between CHOP‐ and COP‐based protocols. Severe methodological heterogeneity and retrospective selection bias prevent definitive conclusions regarding long‐term survival, emphasizing the critical need for homogeneous, prospective randomized trials utilizing standardized reporting guidelines.
